Particular products and byproducts of naturally occurring metabolic processes in cells are used in many branches of industry, including the food industry, the animal feed industry, the cosmetics industry and the pharmaceutical industry. These molecules which are collectively referred to as “fine chemicals” comprise organic acids, both proteinogenic and nonproteinogenic amino acids, nucleotides and nucleosides, lipids and fatty acids, diols, carbohydrates, aromatic compounds, vitamins, cofactors and enzymes. They are best produced by means of cultivating, on a large scale, bacteria which have been developed to produce and secrete large amounts of the molecule desired in each particular case. An organism which is particularly suitable for this purpose is Corynebacterium glutamicum, a Gram-positive nonpathogenic bacterium. Using strain selection, a number of mutant strains have been developed which produce various desirable compounds. The selection of strains which are improved with respect to the production of a particular molecule is, however, a time-consuming and difficult process.